Resorcinol process

ABSTRACT

Resorcinol is produced from metaxylene by dichlorinating metaxylene, oxidizing the resulting 2,4- and 4,6- dichlorinated metaxylenes to produce dichloroisophthalic acids, reacting the acids with an alkali metal hydroxide forming the alkali metal salts of the dichloroisophthalic acids, and heating the salts at an elevated temperature in the presence of a limited amount of water.

United States Patent Suzuki 1 *Sept. 2, 1975 [5 RESORCINOL PROCESS 2.563.820 4 1951 Durrugh ct 211 260 515 A 2.727924 12/1955 Pearlman i 260/621 R [75] Inventor: shlgeto Suzuki, Sun Franc1sco. 1727926 2/1955 Kacding Ct 11 560/621 R Cuhf- 2 852.567 9/1958 Burnhurd ct 617 60/621 R 2,999,879 9/1961 Broich ct a1. 60/515 A A Ch h [73] Sslgnee j g zz gz 'g company 3,075,008 1/1963 Girard et a1 260/515 A 3.089.905 5/1963 Wygand 260/621 R Notice: The portion of the term of this 3769998 9/1973 360/63] R patent Subsequent to gem 18 3,760,009 9/1973 Suzuki 260/621 R 1990, has been discluimed. Primarv Iiruminer-Howard T. Mars 7 I y Filed" Jul) 1973 Assistant Emminer-Norman Morgenstern [21] Appl. No.: 380,413 Attorney Agent, or FirmG. F. Magdeburger; John Related U.S. Application Data C0ntinuziti0n-in-purt of Ser. No. 5,121, Jun. 224

1970 Pat. No. 3,760,008.

U.S. C1. 260/62! R; 260/524 R int. C1. C07C 29/00 Field of Search 260/515 A, 621 R, 629.

260/524 Rt 650 R References Cited UNITED STATES PATENTS 12/1929 Hale ct 211 260/621 R 9/1932 Britton 260/515 A Stoner Jr.; T. G. DeJonghe [57] ABSTRACT Resorcinol is produced from metaxylene by dichlorinating metaxylene. oxidizing the resulting 2.4- and 4.6 dichlo'rinated metaxylenes to produce dichloroisophthalic acids, reacting the acids with an alkali metal hydroxide forming the alkali metal salts of the dichloroisopht'halic acids. and heating the salts at an elevated temperature in the presence of a limited amount of water.

3' Claims, No Drawings 1 RESORCINOL aocess CROSS REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of copending application Ser. No. 5,121, filed .Ian. 22, 1970, now US. Pat. No. 3,760,008.

FIELD OF THE INVENTION This invention relates to a novel process for the production of resorcinol, particularly from alkali metal salts of 2.4- and/or 4,6-dichloroisophthalic acid, which are formed by chlorinating metaxylene and then oxidizing the 2,4- and 4,6-dichlorometaxylene product.

BACKGROUND OF THE INVENTION It is known in the art to prepare resorcinol by the caustic fusion of the salts of 1,3-benzene disulfonic acid. There are a number of disadvantages incidental to this fusion reaction system, including mixing problems, poor heat transfer, and the like. Dilution with water does not lessen these problems, for the addition of water adversely affects the desired reaction.

THE INVENTION It has now been found that resorcinol can be prepared by heating a mixture of an alkali metal salt of 2,4 and/or 4,6- dichloroisophthalic acid, alkali metal hydroxide and water at a temperature in the range from about 150C. to 270C, preferably 190C. to 210C, for a period in the range from about 0.2 to 2 hours, and acidifying the resulting reaction product mixture. Preferably the reaction is promoted by the presence of a copper catalyst in the reaction mixture. Surprisingly, the presence of water in the reaction mixture does not adversely affect the reaction, provided that the relative amount added is not too great. It appears, on a molecular basis, that the amount of water in the reaction mix ture should not materially exceed the amount of the base and that the presence of a large relative amount of water operates detrimentally by reducing the basic strength of the hydroxide in the reaction mixture. For each mol of the salt, the reaction mixture should contain an amount of the hydroxide in the range from about 4 to mols, preferably 6-14 mols. Although the amount of water which can be tolerated in the present process is small, nevertheless it is sufficient to alleviate the aforementioned problems incidental to the ordinary fusion reaction system.

The production of resorcinol by the present process is surprising in view of the art. U.S. Pat. No. 2,439,237 discloses that the treatment of polyhalo-substituted phthalic acid with a base yields polyhalobenzoic acid or polyhalobenzene. Apparently, in view of the present discovery, the geometric relationship of the carboxyl groups of a halo-substituted benzene dicarboxylate salt or acid drastically alters the course of and the products from displacements on aromatic carbon atoms.

The products obtained from halo-substituted phthalates (ortho carboxyl relationship) are different from those obtained from halo-substituted isophthalates (meta carboxyl relationship). The former yield halosubstituted benzoic acid and/or halo-substituted-benzene, whereas the latter yield resorcinol.

A further conflicting factor in the present displacement reactions on aromatic carbon atoms in addition to the aforementioned geometric effect is associated with the pH of the reaction medium. Apparently pH plays an important role in displacements on-aromatic.

CHLORZ'INYATION AND OXIDATlON OF METAXYLENE Resorcinol is a well-known article of commerce. The 2,4- and 4,6-dichloroisophthalic acids, on the other hand, while not of particular commercial importance, are readily prepared from metaxylene. Metaxylene is readily chlorinated to 2,4-' and 4,6-dichloro-l,3- dimethylbenzene in the presence of chlorine gas and Fecl 'at temperatures from 0 to C., preferably from 10 to 30C. The reaction is also preferably carried out in the absence of light, in order to prevent chlorination of the alkylgroup. See, for example, US. Pat. No.,3,035,l03, in which paraxylene in a similar reaction is chlorinated :to produce 2,5- dichloro-l ,4- dimethylbenzene. The resulting 2,4- and 4,6-dichloro- 1,3-dimethylbenzene isomers are readily separated from the reaction mixture using well-known distillation apparatus and techniques.

The 2,4- and 4,6-dichloroisophthalic acids are then prepared from the corresponding dichloro-metaxylenes (see, for example, US. Pat. No. 2,881,224).by conventional oxidation reactions, such as by the use of potassium permanganate, aqueous nitric acid and the like oxidation agents. Dichlorometaxylenemay also be oxidized to'dichloroisophthalic acid by the well-known cobalt-catalyzed, liquid-phase air oxidation processes.

PREFERRED EMBODIM ENT Dichloroisophthalic acid, aqueous sodiumhydroxide, and cuprous oxide are charged to a pressure autoclave fitted for mixing. The amounts of each component are proportioned to yield a reaction mixture having the relative molecular amounts of dichloroisophthalate salt, sodium hydroxide, water and copper catalyst of 1:13: 13:0.16, respectively. The autoclave pluscharge in the liquid phase are heated at a temperature of 2002l()C. for about 1 hour. The resulting reaction mixture is then cooled and acidified bydissolving carbon dioxide gas in the mixture. The liberated resorcinol is then removed by extraction with a suitable organic solvent, for example ethyl ether, and recovered by distillation. I i

The aqueous solution remaining after removal of the resorcinol contains a minor amount of reaction intermediates, mainly monochlorohydroxybenzene carboxylates and sodium bicarbonate from the main reaction (2 mols of sodium bicarbonate for each mol of resorcinol produced) and from excess sodium hydroxide. This solution is regenerated for recycle to the process by the addition of calcium oxide and filtration to remove the insoluble calcium carbonate formed in the regeneration stage as well as some of the sodium chloride, ie.

that amount in excess of solubility. After additions of the base and water to adjust for mechanical losses in THE REACTION EQUATIONS V The chemical conversions effected in the process of the invention may be summarized as follows: i

l. C.,H (CO Na) Cl- 4NaOH m-C.;H,(ONa).

2NaCl 2NaHCO;, 2. NaHCO NaOH Na. ,CO H 0 3. m-C,,l-l ,(ONa) 2C0: 2H. ,O nz-CgH (OH)- ZNaHCO 4. Na CO CO H O 2NaHCO 5. NaHCO Ca0 NaOH CaCO l Since both the 2,4- and 4,6-dichloroisophthalic acid isomers have chlorines in a meta relationship to one another, they both produce resorcinol by the process of this invention.

TEMPERATURE The present process may be carried out over a range of temperatures with the usual reaction rate effect, i.e., the rate doubles for about each C. incremental increase. At 150C. there is an appreciable rate of resorcinol production. In the range 240270C., on the other hand, one or more side reactions are experienced in which resorcinol is converted to undesirable byproduct(s). Best results, in general, obtain at a temperature in the range 1902 10C. after a period of about one hour. Satisfactory reaction temperatures in general are in the range above 150C. and below 240270C.

HYDROXIDE REACTANT In order to effect the displacement of chloride and carboxyl (decarboxylation) groups herein, an exceptionally strong basic medium is required. The alkali metal hydroxides in general satisfy this need. In particular. sodium, potassium and lithium hydroxides and mixtures thereof are useful. For reasons of cost, sodium hydroxide is preferred.

For each mol of the dichloroisophthalate salt present in the reaction mixture (see equation 1 above), at least 4 mols of the alkali metal base is necessary for the satisfaction of the stoichiometric requirement. A substantial excess of the base should be present in order to reduce a polymer-producing side reaction to a satisfactory level. For this purpose, for each mol of salt feed at least 6 mols of base should be present. Best results, in general, obtain when the amount of the base is in the range 10-14 mols per mol of the dichloroisophthalate. Larger relative amounts, for example as much as mols and more, may be employed.

AClDlFlCATlON Acids in general having an acid strength greater than resorcinol are suitable for the liberation of resorcinol from its alkali metal salt. Mineral acids are satisfactory because of the low cost. However, carbon dioxide (carbonic acid) is preferred as an acidifier because its use permits regeneration of the excess alkali metal hydroxide and an easy control of pH in the range 6-7 (see reaction equations above). This pH is sufficient to free resorcinol but does not liberate minor amounts of unconverted carboxylate salt feed or intermediates which may be present in the acidified reaction product mixture.

WATER DILUENT From an inspection of equation 1 above, water does not appear to be a reactant in the reaction system.

. 4 However. in the absence of water the results are poor and the processing is difficult.-Mixing and local overheating effects in particular are not good. At least about 0.5 mol of water per mol of hydroxide should be present in the mixture. An excess of water relative to the hydroxide. on the other hand, adversely affects the desired reaction. When the mol ratio of water to hydroxide exceeds about 1 to l, the results become progressively poorer as the ratio becomes larger. From this fact. it is inferred that amounts of water substantially in excess of a 1:1 ratio reduces the basicity of the hydroxide reagent. Useful results are achieved when the water-to-hydroxide ratio is below about 9, but for satisfactory conversions of the dichloroisophthalate salt to resorcinol this ratio should not exceed about 3-5; and, in general, for the best results, for each mol of hydroxide in the reaction mixture the amount of water should be in the range 1 to 3 mols, preferably 1 mol, of water.

Along with water, if desired, methanol and ethanol may be added to the reaction system as diluents. However, because of the relatively lower boiling points of these alcohols, their presence in the system results in higher system pressures. Similarly, dimethylsulfoxide may also be used as a diluent (see, for example, U.S. Pat. No. 3,481,991 for the present displacement reaction, but such use complicates the resorcinol recovery stage and hence is not a preferred mode.

REACTION PROMOTERS Resorcinol is produced by the process herein in the absence of catalysts. The presence in the reaction medium of a copper compound, however, is beneficial. Copper compounds, in general, which convert to oxide(s) of copper in the presence of strong alkali metal hydroxides are useful promoters for the reaction. Thus, representative promoters suitable for use herein include cuprous oxide, copper chlorides, carboxylates, nitrates, sulfates, acetates, and the like copper compounds.

Trace amounts of copper oxide are beneficial. Satisfactory amounts are in the range 0.01 to 0.25 mol per mol of the dichloroisophthalate salt. Larger relative amounts may be used, but cost becomes a factor. The preferred range is 0.05 to 0.2 mols of promoter (based upon copper) per mol of the dichloroisophthalate feed.

The following examples are for the further illustration of the invention.

EXAMPLES EXAMPLE 1 Chlorination of Metaxylene A 300-m1, 3-necked, round-bottomed flask covered with aluminum foil and equipped with a stirrer, a gas inlet tube, a thermometer, and a condenser exhausting into an aqueous caustic solution was charged with 106.2 g (1.0 mol) of metaxylene and 2.0 g of ferric chloride. Chlorine gas was added at a rate of 250 ml per minute along with nitrogen at 7 ml per minute. During this time, 171 minutes, the temperature was maintained at 8 to 12C. At the end of the time, nitrogen at 300 ml/minute was passed through the reaction mixture for 15 minutes. Then the reaction mixture was washed with 2 l00-ml portions of water and was dried over magnesium sulfate. The dried material weighed 176.5 g. A nuclear magnetic resonance analysis showed only ring chlorination products.

. 5 The reaction mixture was distilled at 10 mm Hg pressure in a 30-inch tantalum spiral column. The results were as follows:

Analysis of Fraction 4 showed it to be a mixture of 4,6-dichloro-l,3-dimethylbenzene and 2,4-dichloro- 1,3-dimethylbenzene in a 70:30 ratio, respectively.

(0.05 mol) of dichloroisophthalic acid (from Example.

2, 14 g (0.35 mol) of sodium hydroxide. and 33 g of water. The reactor was sealed. rocked, and heated at 232 to 252C. for 40 minutes. During this time, the pressure was in the range of 300500 psig. Then the reactor was cooled. and thecontents removed. The reaction mixture was acidified to pH 1 with concentrated hydrochloric acid. The acid solution was extracted with 3 400-ml portions of ether, which were combined and washed with aqueous sodium bicarbonate. Then the ether portion was extracted with 200 ml of a 5% caustic solution. This ether solution was dried over magnesium sulfate. The ether was removed by evaporation to give 4.6 g of crude product which contained 1.5 g of resorcinol (32%) and 3.1 g of metachlorophenol.

The aqueous bicarbonate extract and the aqueous caustic extract were acidified with hydrochloric acid, extracted with ether, and the ether extracts evaporated to dryness to give 2.0 g of dichloroisophthalic acid, in

EXAMPLE 2 Oxidation of Dichlorometaxylene 3 1 dlcatmg an 83% conversion.

A 5-liter, round-bottomed flask equipped with a stir- Similar equipment and procedures were utilized in rer, thermometer, and a reflux condenser was charged Examples 4l0. The conditions and results of Examwith 68 grams (0.39 mol) of dichlorometaxylene (Fracples 3l are listed in Table [1 below.

TABLE ll Ratio Ratio Yield Ex. Na DCl P NaOH Base: H20 H20: Catalyst, Temp. Time. Con vcr- Resorcinol, No. Mols Type Mols Na .DClP Mols Base Wt. 7: Min. sion, 7! Mol 1 3 0.05 Mix 0.25 50 2.2 4.0 250 30 s3 32 4 0.10 4,6 0.60 6.0 3.0 5.0 (11.0. 10 200-20s 45 90 64 5 0.09 4,61- 0.62 70 3.0 5.0 200 60 94 67 6 0.0x 4 0.50 6.2 2.5 5.0 170-177 60 77 70 7 0.06 4 0.45 7.5 1.6 3.6 225-229 30 94 51 s 0.10 46 1.30 13.0 3.6 3.3 200-212 60 xx so 9 0.30 4 3.00 13.0 3.0 1.0 200-212 60 x9 96 10 0.10 2.4- 1.30 13.0 3.5 2.7 zoo-x 60 93 97 Dichloroisu hthalate Based on DClP "70% -11 Z,4-D('|P tion 4 of Example 1), 272 g (l.72 mols) of potassium The data in the above examples clearly establish that permanganate and 2,500 ml of water. This mixture was alkali metal salts of 2,4- and 4,6-dichloroisophthalic refluxed for 31 hours. Then an additional 62 g (0.39 acid and mixtures thereof are effectively converted to mol) of potassium permanganate was added and refluxresorcinol by the novel process herein described. ing was continued for 8 more hours. Again, 30 g (0.19 It is to be understood that the invention is in no way mol) of potassium permanganate was added, and limited by the specific examples given herein and that fluxing was continued for 28 hours. After adding 600 m ny fi i n n variations y be m de i hml of water, 1,900 ml were removed from the flask by out departing from the Splrit and Scope of the mvemive i i l i contribution as set forth in the following claims.

The reaction mixture was filtered while hot. After What is claimediisi cooling, both the distillate and the filtrate were ex- A method for the P1Oductlcm 0f resorcinol tracted separately with hexane. The hexane extracts prlsmgf were combined and dried over magnesium sulfate. The dlchlormatlng meta'Xylene m h Phase dried extracts were placed on a hot plate and the hexunder reactlorl Condmons effecnvevto produce a ane removed by evaporation to leave 5.6 g of diand 4-6dlchloromemxylene mlxture and covering the 2,4- and 4.6-dichlorometaxylene mixture;

oxidizing the recovered 2,4- and 4,6- dichlorometaxylene mixture under reaction conditions effective to produce the corresponding dichloroisophthalic acid isomeric mixture;

. reacting the acid with an alkali metal hydroxide by heating a mixture of the reactants in the liquid phase in the presence of water wherein the heating is above about C. and below about 270C. wherein for each mol of the resulting alkali metal salt of the acid the mixture contains an amount of the hydroxide in the range from about 4 to 20 mols.

7 s and wherein for-each mol of the hydroxide the mix- 3.flhe process as in claim 1 further characterized in ture contains an amount of water in the range from that resorcinol is recovered from the resulting aqueous about 0.5 to below about 9 mols; and reaction mixture by: d. acidifying the resulting reaction product mixture. at. Acidifying the mixture with carbon dioxide; and 2. The method as in claim 1 further characterized in 5 b. Separating the resorcinol from the acidified mixthat the reaction of step (c) is promoted by copper oxture by extraction with ether. id =l 

1. A METHOD FOR THE PRODUCTION OF RESORICINOL COMPRISING: A. DICHLORINATING METAXYLENE IN THE LIQUID PHASE UNDER REACTION CONDITIONS EFFECTIVE TO PRODUCE A 2,4- AND 4,6DICHLOROMETALYENE MIXTURE AND RECOVERING THE 2,4- AND 4,6-DICHLOROMETHYLENE MIXTURE, B. OXIDIZING THE RECOVERED 2,4- AND 4,6-DICHLOROMETAXYLENE MIXTURE UNDER REACTION CONDITIONS EFFECTIVE TO PRODUCE THE CORRESPONDING DICHLOROISOPHTHALIC ACID ISOMERIC MIXTURE, C. REACTING THE ACID WITH AN ALKALI METAL HYDROXIDE BY HEATING A MIXTURE OF THE REACTANTS IN THE LIQUID PHASE IN THE PRESENCE OF WATER WHEREIN THE HEATING IS ABOVE ABOUT 150*C. AND BELOW ABOUT 270*C, WHEREIN FOR EACH MOL OF THE RESULTING ALKALI METAL SALT OF THE ACID THE MIXTURE CONTAINS AN MOUNT OF THE HYDROXIDE IN THE RANGE FROM ABOUT 4 TO 20 MOLS, AND WHEREIN FOR EACH MOL OF THE HYDROXIDE THE MIXTURE CONTAINS AN AMOUNT OF WATER IN THE RANGE FROM ABOUR 0.5 TO BELOW ABOUT 9 MOLS, AND D. ACIDIFYING THE RESULTING REACTION PRODUCT MIXTURE
 2. The method as in claim 1 further characterized in that the reaction of step (c) is promoted by copper oxide.
 3. The process as in claim 1 further characterized in that resorcinol is recovered from the resulting aqueous reaction mixture by: a. Acidifying the mixture with carbon dioxide; and b. Separating the resorcinol from the acidified mixture by extraction with ether. 